I am an atheist, but I will try to address my understanding from both "their is a supernatural being that knows how everyone should behave" and the atheist standpoints.
There is a being that judges humans good or badLet's assume that one of the religions that says there is a being that knows right from wrong, e.g. Santa Claus, is right. Whatever that being says is the ultimate moral truth is just that.
So then that would mean there are objective morals.
OK, but since the being is intangible, and not everyone believes in that being, how can a human know what is and isn't moral.
Those who have faith say that their being (or beings) has instructed them in the way. There is more than one faith, so which is right? Also, faith comes from within, and therefore is subjective.
For some reason humans have to decide which of the beings is correct by themselves. Thus, from a human standpoint, morals must be subjective, because humans cannot objectively know the right way from the wrong way, because if that could be shown then we would all know if what we were doing was objectively right or wrong. We could all agree about it, so we would know if someone was "bad" or not. Since we don't all agree about what is right or wrong, bad or good, then the true path isn't self evident.
Atheist are rightLet's assume there is no being that has moral oversight of the universe. So, then morality must be subjective. Each person has their own idea of right and wrong.
If that is the case then why do we have laws? Why do we have power structures? Why are there any rules at all in society?
Two reasons: to aid in coöperation and to reïnforce the power structure.
In the society of the UK as I am writing this, if I want something somebody else owns:
- I can buy it, if they are willing to sell it
- I can be given it, if they are willing to give it away
- I can steal it.
In the context of stealing, it is seen as morally incorrect because it reduces the likelihood of coöperation in the future (people protect their possessions more and don't share as much), and also because people with useful possession have power over those who need to use them, and so stealing breaks the power structure.
(This is also why gift giving to a stranger is seen as weaker than selling things to them, because without an exchange of money, the power structure is changed, so the person who has given is perceived as weaker and weakness is perceived as bad.)
So are increasing coöperation and reïnforcing power structures moral absolutes? Should we always seek to do these things?
If being morally correct is a choice, then no.
Sometimes increasing coöperation will change the current power structure. Sometimes enforcing the current power structure will decrease coöperation.
Let's say, for example, you want to increase the coöperation of environmentalists with oil prospectors.
Environmentalists (E) believe oil prospectors (OP) are wrong because E believe that the results of the OP will damage the environment, which is anti-coöperation, as it hurts lots of people, and will result in a complete collapse of the current power systems.
OP believe that E are wrong because OP's results keeps the current power systems running and therefore is in maximum coöperation.
Forcing one to coöperate with the other will cause a change in the power structure, because they will both have to give way, and so lose power.
Humans have very low predictive power. We struggle to accurately predict the repercussions of anything we do further ahead than a year, and most of the time we don't even try for further than a moment.
That's natural, due to how many moving parts our universe has.
Neither OP nor E can be sure about the long term outcome of their actions, so their moral stances are both relative to their understandings of the situation.
ConclusionIn the grand scheme of things, due to the human race's lack of understanding of the universe, moral decision is relative, as we don't know if the universe is for anything, so cannot know if our actions improve or impede the chance of universal success.
If the universe isn't for anything, then morals are a personal thing.
If the universe is under the moral purview of some being or beings then absolute morals are their concern, but not something we can divine.